U.S. patent application number 10/534351 was filed with the patent office on 2006-07-13 for cleaning composition and method of cleaning therewith.
This patent application is currently assigned to WAKO PURE CHEMICAL INDUSTRIES. Invention is credited to Ichiro Hayashida, Takehisa Kato, Hironori Mizuta.
Application Number | 20060154838 10/534351 |
Document ID | / |
Family ID | 32310455 |
Filed Date | 2006-07-13 |
United States Patent
Application |
20060154838 |
Kind Code |
A1 |
Hayashida; Ichiro ; et
al. |
July 13, 2006 |
Cleaning composition and method of cleaning therewith
Abstract
The present invention relates to a liquid cleaner for a
semiconductor substrate on which metal wiring may be provided,
comprising each component of a chelating agent or a salt thereof
shown by the following general formula (1), an alkaline compound
and pure water, wherein pH is 8 to 13: ##STR1## (wherein, Y.sup.1
and Y.sup.2 are lower alkylene groups, n is an integer of 0 to 4,
at least 4 of R.sup.1 to R.sup.4 and n R.sup.5s are alkyl groups
having phosphonic acid group(s) and the rest are alkyl groups) and
a cleaning method using the same. The present invention provides a
liquid cleaner which can efficiently remove fine particles or
impurities derived from various metals at semiconductor substrate
surface, even when used after a process adopting an alkaline
polishing agent or alkaline etching liquid, without generating
problems of causing difficult-to-remove gelled particles at the
substrate surface or easy generation of rough semiconductor
substrate surface, and a cleaning method using the same.
Inventors: |
Hayashida; Ichiro; (Saitama,
JP) ; Mizuta; Hironori; (Saitama, JP) ; Kato;
Takehisa; (Saitama, JP) |
Correspondence
Address: |
WESTERMAN, HATTORI, DANIELS & ADRIAN, LLP
1250 CONNECTICUT AVENUE, NW
SUITE 700
WASHINGTON
DC
20036
US
|
Assignee: |
WAKO PURE CHEMICAL
INDUSTRIES
OSAKA-SHI
JP
|
Family ID: |
32310455 |
Appl. No.: |
10/534351 |
Filed: |
November 7, 2003 |
PCT Filed: |
November 7, 2003 |
PCT NO: |
PCT/JP03/14183 |
371 Date: |
November 7, 2005 |
Current U.S.
Class: |
510/175 ;
134/2 |
Current CPC
Class: |
H01L 21/02052 20130101;
H01L 21/02068 20130101; C11D 11/0047 20130101; C11D 7/36
20130101 |
Class at
Publication: |
510/175 ;
134/002 |
International
Class: |
C23G 1/00 20060101
C23G001/00; C11D 7/32 20060101 C11D007/32 |
Foreign Application Data
Date |
Code |
Application Number |
Nov 8, 2002 |
JP |
2002-324853 |
Claims
1. A liquid cleaner for a semiconductor substrate on which metal
wiring may be provided, comprising each component of a chelating
agent or a salt thereof shown by the following general formula (1),
an alkaline compound and pure water, wherein pH is 8 to 13.
##STR4## (wherein, Y.sup.1 and Y.sup.2 are lower alkylene groups, n
is an integer of 0 to 4, at least 4 of R.sup.1 to R.sup.4 and n
R.sup.5s are alkyl groups having phosphonic acid group(s) and the
rest are alkyl groups).
2. The liquid cleaner according to claim 1, wherein, Y.sup.1 and
Y.sup.2 in the chelating agent shown by the general formula (1) are
alkylene groups having 1 to 4 carbon atoms and alkyl groups in
alkyl groups which may have phosphonic acid group(s) relevant to
R.sup.1 to R.sup.4 and n R.sup.5s are alkyl groups having 1 to 4
carbon atoms.
3. The liquid cleaner according to claim 1, wherein the chelating
agent or a salt thereof is at least one kind selected from the
group consisting of ethylenediaminetetraethylenephosphonic acid,
ethylenediaminetetraethylenephosphonic acid ammonium salt,
ethylenediaminetetraethylenephosphonic acid potassium salt,
ethylenediaminetetraethylenephosphonic acid sodium salt,
ethylenediaminetetraethylenephosphonic acid lithium salt,
ethylenediaminetetramethylenephosphonic acid,
ethylenediaminetetramethylenephosphonic acid ammonium salt,
ethylenediaminetetramethylenephosphonic acid potassium salt,
ethylenediaminetetramethylenephosphonic acid sodium salt,
ethylenediaminetetramethylenephosphonic acid lithium salt,
diethylenetriaminepentaethylenephosphonic acid,
diethylenetriaminepentamethylenephosphonic acid,
diethylenetriaminepentamethylenephosphonic acid ammonium salt,
diethylenetriaminepentamethylenephosphonic acid potassium salt,
diethylenetriaminepentamethylenephosphonic acid sodium salt,
diethylenetriaminepentamethylenephosphonic acid lithium salt,
triethylenetetraminehexaethylenephosphonic acid,
triethylenetetraminehexamethylenephosphonic acid,
triethylenetetraminehexamethylenephosphonic acid ammonium salt,
triethylenetetraminehexamethylenephosphonic acid potassium salt,
triethylenetetraminehexamethylenephosphonic acid sodium salt,
triethylenetetraminehexamethylenephosphonic acid lithium salt,
propanediaminetetraethylenephosphonic acid,
propanediaminetetramethylenephosphonic acid,
propanediaminetetramethylenephosphonic acid ammonium salt,
propanediaminetetramethylenephosphonic acid potassium salt,
propanediaminetetramethylenephosphonic acid sodium salt and
propanediaminetetramethylenephosphonic acid lithium salt.
4. The liquid cleaner according to claim 1, wherein the alkaline
compound is at least one kind selected from the group consisting of
hydroxides of alkaline metals, carbonate salts of alkaline metals,
aqueous ammonia solution or salts thereof, piperazine or
derivatives thereof and guanidine or salts thereof.
5. The liquid cleaner according to claim 1, further comprising a
buffering agent.
6. The liquid cleaner according to claim 5, wherein the buffering
agent is one selected from boric acid and a good's buffer.
7. A method for cleaning a semiconductor substrate, which comprises
the semiconductor substrate, on which metal wiring may be provided,
is cleaned with a liquid cleaner of claim 1.
Description
FIELD OF THE INVENTION
[0001] The present invention relates to a liquid cleaner for a
semiconductor substrate, which may have metal wiring, after
polishing treatment, etching treatment, CMP treatment, and the like
and a method for cleaning a semiconductor substrate using the
same.
BACKGROUND ART
[0002] In preparation of semiconductor, various treatments are
repeated such as smoothing of silicon wafer substrate surface,
etching to laminate various layers on the substrate and smoothing
of the surface after lamination.
[0003] In each of these treatment processes, fine particles such as
polishing particles, impurities derived from various metals and
foreign substances derived from slurry adhere to semiconductor
substrate surface. It is known that when semiconductor is
manufactured leaving these impurities as they are, risk increases
for semiconductor finally obtained to be unsatisfactory.
[0004] Therefore, a process to a clean semiconductor substrate
surface after these various treatment processes, so to speak a
cleaning process is performed.
[0005] Liquid property (pH) of a liquid cleaner used in this
cleaning process is said preferably to have nearly the same degree
as in various treatment solutions used in a prior process. That is,
too rapid change in pH at substrate surface in cleaning the
semiconductor substrate surface causes gelling of particles at the
semiconductor substrate surface, which makes removal difficult or
easily generates roughness of semiconductor substrate surface.
Therefore, it is preferable that a liquid cleaner used after a
process, adopting an alkaline polishing agent or an alkaline
etching liquid, is an alkaline type.
[0006] However, when cleaning is performed using a conventional
liquid cleaner (for example, the liquid cleaners disclosed in
JP-A-5-275405, WO 01/071789, JP-A-10-072594, JP-A-2002-020787,
JP-A-11-131093-, JP-A-3-219000, etc.), ability to remove impurity
derived from various metals (metals themselves, oxides thereof,
hydroxides thereof, etc.), which are adhered to semiconductor
substrate surface, was not sufficient and further improvement has
been required.
[0007] The present invention is completed considering such problems
of conventional technology. The present invention aims at providing
an alkaline liquid cleaner which can efficiently remove fine
particles or impurities derived from various metals at
semiconductor substrate surface, even when used after a process
adopting an alkaline polishing agent or alkaline etching liquid,
without generating problems of causing difficult-to-remove gelled
particles at the substrate surface or easy generation of rough
semiconductor substrate surface.
DISCLOSURE OF THE INVENTION
[0008] The present invention is composed of the following to attain
the above-described objectives: (1) a liquid cleaner for a
semiconductor substrate on which metal wiring may be provided,
comprising each component of a chelating agent or a salt thereof
shown by the following general formula (1), an alkaline compound
and pure water, wherein pH is 8 to 13. ##STR2## (wherein, Y.sup.1
and Y.sup.2 are lower alkylene groups, n is an integer of 0 to 4,
at least 4 of R.sup.1 to R.sup.4 and n R.sup.5s are alkyl groups
having phosphonic acid group(s) and the rest are alkyl groups; and
(2) a method for cleaning a semiconductor substrate, which
comprises the semiconductor substrate, on which metal wiring may be
provided, is cleaned with a liquid cleaner of the above (1).
BEST MODE FOR CARRYING OUT THE INVENTION
[0009] A liquid cleaner used in cleaning process contains a
chelating agent or a salt thereof shown by the following general
formula (1), an alkaline compound and pure water: ##STR3##
(wherein, Y.sup.1 and Y.sup.2 are lower alkylene groups, n is an
integer of 0 to 4, at least 4 of R.sup.1 to R.sup.4 and n R.sup.5s
are alkyl groups having phosphonic acid group(s) and the rest are
alkyl groups)
[0010] The lower alkylene group here is preferably linear or
branched one having 1-4 carbon atoms, and specifically includes,
for example, a methylene group, an ethylene group, a propylene
group, a methylmethylene group, a methylethylene group, an
ethylmethylene group, a butylene group, a methylpropylene group, an
ethylethylene group, etc.
[0011] The alkyl group in the alkyl group which may have phosphonic
acid group(s) is preferably linear or branched one having 1-4
carbon atoms, and specifically includes, for example, a methyl
group, an ethyl group, a n-propyl group, an isopropyl group, a
n-butyl group, an isobutyl group, a sec-butyl group, a tert-butyl
group, etc. Number of phosphonic acid groups which these alkyl
groups may have is usually 1 to 2 and preferably 1.
[0012] The chelating agent or the salt thereof shown by the general
formula (1) is contained to capture and remove metal impurity
adhered and remained at semiconductor substrate surface which may
have metal wiring, after polishing treatment, etching treatment,
CMP treatment, and the like. Metal impurity includes one derived
from a transition metal such as iron (Fe), nickel (Ni), copper,
etc. and an alkaline earth metal such as calcium (Ca), magnesium
(Mg), etc, for example these metals themselves, oxides thereof,
hydroxides thereof, etc. The chelating agent or the salt thereof
shown by the general formula (1) removes metal impurity by forming
stable complex ions with these metals.
[0013] The salt of the chelating agent includes an alkaline metal
salt such as a lithium salt, a sodium salt, a potassium salt, etc.
and an ammonium salt.
[0014] The chelating agent or the salt thereof specifically
includes ethylenediaminetetraethylenephosophonic acid,
ethylenediaminetetraethylenephosophonic acid ammonium salt,
ethylenediaminetetraethylenephosophonic acid potassium salt,
ethylenediaminetetraethylenephosophonic acid sodium salt,
ethylenediaminetetraethylenephosophonic acid lithium salt,
ethylenediaminetetramethylenephosophonic acid,
ethylenediaminetetramethylenephosophonic acid ammonium salt,
ethylenediaminetetramethylenephosophonic acid potassium salt,
ethylenediaminetetramethylenephosophonic acid sodium salt,
ethylenediaminetetramethylenephosophonic acid lithium salt,
diethylenetriaminepentaethylenephosophonic acid, diethylenetriamine
pentamethylenephosphonic acid, diethylenetriamine
pentamethylenephosphonic acid ammonium salt, diethylenetriamine
pentamethylenephosphonic acid potassium salt, diethylenetriamine
pentamethylenephosphonic acid sodium salt, diethylenetriamine
pentamethylenephosphonic acid lithium salt, triethylenetetramine
hexaethylenephosphonic acid, triethylenetetramine
hexa(methylenephosphonic acid, triethylenetetramine
hexamethylenephosphonic acid ammonium salt, triethylenetetramine
hexamethylenephosphonic acid potassium salt, triethylenetetramine
hexamethylenephosphonic acid sodium salt, triethylenetetramine
hexamethylenephosphonic acid lithium salt,
propanediaminetetraethylenephosphonic acid,
propanediaminetetramethylenephosphonic acid,
propanediaminetetramethylenephosphonic acid ammonium salt,
propanediaminetetramethylenephosphonic acid potassium salt,
propanediaminetetramethylenephosphonic acid sodium salt,
propanediaminetetramethylenephosphonic acid lithium salt, etc. They
may be used alone or optionally in combination of two or more
compounds.
[0015] Among these chelating agents or salts thereof, those shown
by the above general formula (1), wherein all of R.sup.1 to R.sup.4
and n R.sup.5s are alkyl groups having phosphonic acid group(s) are
preferable due to having high potential to form a complex with
metal impurity. In the above general formula (1), "n" is preferably
an integer of 0 to 2 in view of production easiness.
[0016] More preferable one, therefore, includes at least one kind
selected from the group consisting of
ethylenediaminetetramethylenephosophonic acid (hereinafter
abbreviated as "EDTPO". Names in parenthesis after compound names
hereinafter show abbreviated symbols thereof.),
ethylenediaminetetramethylenephosophonic acid ammonium salt,
ethylenediaminetetramethylenephosophonic acid potassium salt,
ethylenediaminetetramethylenephosophonic acid sodium salt,
ethylenediaminetetramethylenephosophonic acid lithium salt,
diethylenetriaminepentaethylenephosophonic acid (DEPPO),
triethylenetetraminehexaethylenephophonic acid (TETHP),
propanediaminetetraethylenephosphonic acid (PDTMP), etc. Among
these, at least one kind selected from the group consisting of
EDTPO, DEPPO, TETHP and PDTMP is particularly preferable.
[0017] An amount of the chelating agent or the salt thereof in a
cleaning composition is, as lower limit, preferably not lower than
0.001% by weight, more preferably not lower than 0.005% by weight
and most preferably not lower than 0.01% by weight, while as upper
limit, preferably not higher than 20% by weight, more preferably
not higher than 15% by weight and most preferably not higher than
10% by weight.
[0018] The alkaline compound is used to minimize variation of
liquid property in cleaning performed as post-process such as
polishing treatment, etching treatment and CMP treatment, and the
like, using various alkaline agents. In view of easiness of
composition handling, liquid property is preferably, as lower
limit, not lower than 8, more preferably not lower than 9 and most
preferably not lower than 10, while as upper limit, preferably not
higher than 13, more preferably not higher than 12 and most
preferably not higher than 11.
[0019] That is, in cleaning of semiconductor substrate surface
which may have metal wiring on the surface, after treatment
processes of polishing, etching, CMP, and the like, using various
alkaline agents, too rapid change in pH at said substrate surface
causes gelling of polishing compound remanded at the semiconductor
substrate surface, which makes removal difficult. The alkaline
compound is used to effectively suppress such the gelling and
re-adsorption phenomenon of particles such as abrasive grains used
in polishing onto silicon wafer surface due to being adjustable of
zeta-potential of particles to minus side. It is also used to
promote dissociation of a chelating agent and thus accelerate
complex formation reaction with impurity metal.
[0020] An alkaline compound used for this purpose includes alkaline
metal hydroxides such as potassium hydroxide, sodium hydroxide,
lithium hydroxide, etc.; alkaline metal carbonate such as potassium
hydrogen carbonate, potassium carbonate, sodium hydrogen carbonate,
lithium hydrogen carbonate, lithium hydrogen carbonate, etc.;
aqueous ammonia solution or a salt thereof such as ammonium
hydrogen carbonate, ammonium carbonate, etc.; piperazine (any of
anhydrous or six hydrates), or a derivative thereof such as
1-(2-aminoethyl)piperazine, N-methylpiperazine, etc.; guanidine or
a salt thereof such as guanidine carbonate, etc. They may be used
alone or optionally in combination of two or more compounds.
[0021] Among these, particularly preferable one is an alkali metal
hydroxide relatively often used as an alkaline polishing agent,
etching agent, CMP treatment agent, etc. That is, by using these,
generally used as an alkaline polishing agent, etching agent, CMP
treatment agent, and the like before a cleaning process, generation
of insoluble fine particles induced by variation of alkaline
components can be suppressed and damage to substrate surface can be
avoided, along with cleaning effect can be increased.
[0022] An amount of an alkaline compound in liquid cleaner is,
although depending on type thereof, suitably selected from the
range of, as lower limit, generally not lower than 0.1% by weight,
more preferably not lower than 0.5% by weight and most preferably
not lower than 1% by weight, while as upper limit, generally not
higher than 20% by weight, more preferably not higher than 18% by
weight and most preferably not higher than 16% by weight. In more
specifically, in using potassium hydroxide, sodium hydroxide and
guanidine, the lower limit is preferably not lower than 0.1% by
weight, more preferably not lower than 0.5% by weight and further
preferably not lower than 1% by weight, while the upper limit is
preferably not higher than 6% by weight, more preferably not higher
than 5% by weight and further preferably not higher than 4% by
weight; and in using piperazine 6-hydrates, lower limit is
preferably not lower than 0.1% by weight, more preferably not lower
than 2% by weight and further preferably not lower than 5% by
weight, while the upper limit is preferably not higher than 20% by
weight, more preferably not higher than 18% by weight and further
preferably not higher than 16% by weight.
[0023] To the liquid cleaner of the present invention, a suitable
buffering agent may be added to maintain pH in the above-described
range and such a buffering agent includes, for example, a boric
acid or a good's buffer known as a biochemical buffering agent, and
the like. A preferable good's buffer agent includes, for example,
N,N-bis(2-hydroxyethyl)glycine (Bicine),
N-cyclohexyl-3-aminopropane sulfonic acid (CAPS),
N-cyclohexyl-2-hyrdoxy-3-aminopropane sulfonic acid (CAPSO) and
N-cyclohexyl-2-aminoethane sulfonic acid (CHES), and a more
preferable agent includes N-cyclohexyl-3-aminopropane sulfonic acid
(CAPS) or N-cyclohexyl-2-aminoethane sulfonic acid (CHES).
[0024] These buffering agents are used by suitably mixed with the
above-described alkaline compound (such as potassium hydroxide,
sodium hydroxide, etc.) relevant to the present invention so that
pH is in the above-described range (pH8 to 13).
[0025] Concentration of the buffering agent in cleaning liquid of
the present invention in such cases is, as lower limit, generally
not lower than 0.01% by weight, preferably not lower than 0.05% by
weight and more preferably not lower than 0.1% by weight, while as
the upper limit, generally not higher than 10% by weight,
preferably not higher than 5% by weight and more preferably not
higher than 2.0% by weight.
[0026] Pure water is added to dissolve each component of the
chelating agent or the salt thereof and the alkaline compound, and
optionally, the buffering agent. Water with minimum impurity level
is preferable so as not to inhibit action of other components.
Specifically, pure water or ultra-pure water, prepared by removing
foreign substances through a filter after removing impurity ion by
an ion exchange resin, or distilled water, etc. is preferable The
liquid cleaner of the present invention is supplied as a solution
containing each component in the above-described concentration.
This solution may be used for cleaning as it is, however, use by
suitable dilution is preferable in view of balance between cost and
cleaning effect. In use by such dilution, preferable volume ratio
of the liquid cleaner of the present invention and pure water used
for dilution (liquid cleaner: pure water) is 1:1 to 100, more
preferably 1:1 to 80 and most preferably 1:1 to 50.
[0027] The liquid cleaner of the present invention is prepared by
dissolving into water each component of the chelating agent or the
salt thereof relevant to the present invention and the alkaline
compound and optionally, the buffering agent.
[0028] A method for dissolving into water each component of the
chelating agent or the salt thereof relevant to the present
invention and the alkaline compound and optionally, the buffering
agent is not especially limited as long as it is a method for
providing a solution containing these components finally.
[0029] Specifically, these methods include, for example, (1) a
method for directly adding into water the chelating agent or the
salt thereof and the alkaline compound and optionally, the
buffering agent relevant to the present invention, followed by
stirring and dissolving, (2) a method for mixing a solution
containing the chelating agent or the salt thereof relevant to the
present invention and a solution containing the alkaline compound
and, if necessary a solution containing the buffering agent, by
separately dissolving into water the chelating agent or the salt
thereof and the alkaline compound and optionally the buffering
agent relevant to the present invention, or optionally, (3) a
method for mixing a solution containing the chelating agent or the
salt thereof and the buffering agent relevant to the present
invention, obtained by directly adding into water the chelating
agent or the salt thereof and the buffering agent relevant to the
present invention, followed by stirring and dissolving, and a
solution containing the alkaline compound relevant to the present
invention obtained by separately dissolving into water, (4) a
method for mixing a solution containing the alkaline compound and
the buffering agent relevant to the present invention, obtained by
directly adding into water the alkaline compound and the buffering
agent relevant to the present invention, followed by stirring and
dissolving, and a solution containing the chelating agent or the
salt thereof relevant to the present invention obtained by
separately dissolving into water and (5) a method for mixing a
solution containing the chelating agent or the salt thereof and the
alkaline compound relevant to the present invention obtained by
directly adding into water the chelating agent or the salt thereof
and the alkaline compound relevant to the present invention,
followed by stirring and dissolving, and a solution containing the
buffering agent relevant to the present invention obtained by
separately dissolving into water.
[0030] The liquid cleaner of the present invention thus prepared is
preferably subjected to filtration treatment, and the like before
use.
[0031] A cleaning method using the liquid cleaner of the present
invention may be any one as long as the liquid cleaner of the
present invention can be contacted with semiconductor substrate
surface and includes a method for dipping wafer into the liquid
cleaner (dipping treatment), a method for showering or spraying the
liquid cleaner, (single-wafer-based treatment), etc. Cleaning by
the liquid cleaner of the present invention may be combined with a
physical cleaning method such as brush-scrub and a megasonic,
etc.
[0032] A specific method to combine with physical cleaning
includes, for example, a method to apply a physical cleaning after
providing the liquid cleaner of the present invention on the
substrate surface by coating said liquid cleaner on the substrate
surface, a method to apply a physical cleaning after providing the
liquid cleaner of the present invention on the substrate surface by
dipping the substrate in said liquid cleaner, then taking it out of
said liquid cleaner, a method to apply a physical cleaning while a
substrate is dipped in the liquid cleaner of the present invention,
a method to apply a physical cleaning after providing the liquid
cleaner of the present invention on the substrate surface by
showering said liquid cleaner on the substrate surface, or, a
method to apply a physical cleaning while the liquid cleaner of the
present invention is showered on the substrate surface, etc.
[0033] A semiconductor substrate which may have metal wiring on the
surface, suitably applied to cleaning by the liquid cleaner of the
present invention includes, so to speak, silicon wafer, glass
substrate for LCD and PDP, compound semiconductor substrate of such
as GaAs and GaP, printed circuit board, etc.
[0034] Amongthem, the liquid cleaner of the present invention is
useful to silicon wafer, glass substrate for LCD and PDP and
compound semiconductor substrate of such as GaAs and GaP, in
particular, to silicon wafer and compound semiconductor of such as
GaAs and GaP. Further, the liquid cleaner of the present invention
is useful to, among these substrates, substrate on which surface
metal wiring is provided, such as copper, silver, aluminum,
tungsten plug, chromium, gold, and the like, and in particular, to
substrate on which surface copper or silver wiring is provided or
further substrate on which surface copper wiring is provided and is
most useful to semiconductor substrate on which copper wiring is
provided.
[0035] The liquid cleaner of the present invention shows effective
cleaning performance even at room temperature, however, cleaning
effect increases at higher temperature. Therefore, the liquid
cleaner may be used under suitably heated condition. In the case of
use under heating, the liquid cleaner of the present invention is
used generally at 30 to 80.degree. C., preferably at 35 to
70.degree. C. and more preferably at 40 to 60.degree. C.
[0036] Further, the liquid cleaner of the present invention may
contain various assisting components (such as surfactants,
antiseptics, organic solvents, and the like) other than the
above-described components, in the range not to impair effects of
the present invention. However, it is not preferable to add
hydrogen peroxide into the liquid cleaner of the present invention.
That is, when semiconductor substrate on which metal wiring is
provided is subjected to cleaning with a liquid cleaner containing
hydrogen peroxide, said metal wiring surface is oxidized to induce
increase in resistance or disconnection by corrosion, and the like
in high probability and thus general applicability of the liquid
cleaner of the present invention is not secured. Therefore, it is
desirable not to add hydrogen peroxide into the liquid cleaner of
the present invention.
[0037] The addition of surfactant(s) to the liquid cleaner of the
present invention improves hydrophilicity of the liquid cleaner of
the present invention to substrate surface, which in turn improves
synergistic cleaning effect such as removal of metal impurity or
abrasive grain components. A specific surfactant used for this
purpose includes polyoxyethylene dodecyl phenyl ether,
polyoxyethylene polyoxypropylene alkyl ether, polyoxyethylene
acetylenic glycol ether, sodium dodecylbenzene sulfonate, potassium
perfluoroalkyl sulfonate, sodium lauryl sulfate, etc. Use
concentration thereof is, as lower limit, generally not lower than
0.01% by weight, preferably not lower than 0.05% by weight and more
preferably not lower than 0.1% by weight, while as the upper limit,
generally not higher than 5.0% by weight, preferably not higher
than 2.0% by weight and more preferably not higher than 1.0% by
weight.
[0038] As described above in detail, embodiment of the present
invention provides the following effects.
[0039] The chelating agent or the salt thereof contained in the
liquid cleaner has high ability to clean and remove metal impurity
due to more easily formation of stable complex ion with metal
impurity derived from transition metals, and the like, compared
with a conventional chelating agent such as EDTA, etc. Therefore,
in cleaning semiconductor substrate surface which may have metal
wiring at the surface, it can reduce amount of metal impurity
adhered to the surface.
[0040] Furthermore, because complex ion formed by reaction between
metal impurity and the chelating agent or the salt thereof shows
anionic nature, complex ion exhibits electrostatic repulsion
against semiconductor substrate surface having negative zeta
potential, which can suppress re-adherence of metal impurity or
abrasive grain, and the like to substrate surface. This effect can
suppress contamination of semiconductor substrate by impurity
derived from transition metals such as Cu, Fe, Ni, and the like or
alkaline earth metals such as Ca, Mg, etc.
[0041] Because the liquid cleaner of the present invention is
adjusted to alkalescence and thus it can be adjusted to have the
same liquid property as that of an alkaline polishing composition,
etching composition and CMP composition, which then enables to
minimize problems such as gelling of abrasive grains due to pH
shock or roughness of substrate surface and thus can provide high
cleaning effect.
[0042] Hereinbelow, examples and comparative examples are given
below as detailed explanation of the present invention, but the
present invention should not be restricted by these examples.
[0043] In examples, and the like below, concentration of impurity
metal adsorbed and remained at silicon wafer surface was determined
by recovery of impurity metal at silicon wafer surface by a dilute
HF solution and graphite furnace atomic absorption spectrometry
(hereinafter abbreviated as a dilute HF recovery-atomic absorption
method). Furthermore, ultra-pure water was used in liquid
preparation or analysis and HF was also ultra-high purity
reagent.
[0044] Abbreviations used in examples, and the like hereinbelow are
as follows:
[0045] EDTPO: ethylenediaminetetramethylenephosphonic acid
[0046] DEPPO: diethylenetriaminepentaethylenephosphonic acid
[0047] TETHP: triethylenetetraminehexaethylenephosphonic acid
[0048] PDTMP: propanediaminetetraethylenephosphonic acid
[0049] EDA: ethylenediamine
[0050] DETA: diethylenetriamine
[0051] EDTA: ethylenediaminetetraacetic acid
[0052] DTPA: diethylenetriaminepentaacetic acid
[0053] TMAH: tetramethylammonium hydroxide
[0054] CHES: N-cyclohexyl-2-aminoethane sulfonic acid
[0055] CAPS: N-cyclohexyl-3-aminopropane sulfonic acid
EXAMPLES
Example 1
[0056] To an aqueous solution of potassium hydroxide were added
colloidal silica with particle diameter of not larger than 100 nm
to be 15% by weight and 100 ppb of Fe, Cu, Al and Ca nitrates as
metal impurities to prepare an alkaline composition for polishing.
After polishing the surface of 6 inch P-type (100) silicon wafer
with thus prepared contaminated polishing composition, the surface
was rinsed with ultra-pure water. After the silicon wafer was dried
with a spin dryer, residual volume of impurity metals adsorbed to
the silicon wafer surface was measured by a dilute HF
recovery-atomic absorption method.
[0057] Measurement results of adsorption at the silicon surface
were: Fe of 5.times.10.sup.13 atoms/cm.sup.2, Cu of
2.times.10.sup.13 atoms/cm.sup.2, Al of 3.times.10.sup.14
atoms/cm.sup.2 and Ca of 8.times.10.sup.12 atoms/cm.sup.2.
[0058] Pure water was added to liquid cleaners compositions No. 1
to No. 9 of the present invention described in Table 1 to prepare a
solution diluted to 10 to 100 times, in which the silicon wafer
above prepared was dipped at 5.degree. C. for 5 minutes for
washing. After rinsing with ultra-pure water and drying with a spin
dryer, Amounts of impurity metals remained at the silicon wafer
surface was quantitatively measured by the above-described method.
Results are shown in Table 1.
Comparative Example 1
[0059] Silicon wafer contaminated with Fe, Cu, Al and Ca, prepared
similarly as in Example 1 was dipped in solution obtained by
diluting to 10 to 100 times with adding a treatment agent having
composition of No. 10 to No. 14 described in Table 1 to pure water,
or ultra-pure water (No. 15) at 25.degree. C. for 5 minutes for
cleaning, followed by treatment similarly as in Example 1. Results
are shown in Table 1. TABLE-US-00001 TABLE 1 Chelating Conc.
Alkaline Conc. Buffering Cleaning effect (atms/cm.sup.2) No. agent
(%) compound (%) agent pH Fe Cu Al Ca Example 1 1 EDTPO 1 KOH 4 --
13 3 .times. 10.sup.10 8 .times. 10.sup.10 5 .times. 10.sup.10 6
.times. 10.sup.10 2 DEPPO 10 KOH 3 -- 10 6 .times. 10.sup.9 3
.times. 10.sup.10 7 .times. 10.sup.10 3 .times. 10.sup.10 3 TETHP 1
KOH 3 -- 13 2 .times. 10.sup.10 5 .times. 10.sup.10 8 .times.
10.sup.10 2 .times. 10.sup.10 4 PDTMP 3 KOH 0.2 CHES 9 4 .times.
10.sup.9 9 .times. 10.sup.9 2 .times. 10.sup.10 9 .times. 10.sup.9
5 EDTPO 5 KOH 1 -- 10 8 .times. 10.sup.10 4 .times. 10.sup.10 7
.times. 10.sup.10 3 .times. 10.sup.10 6 EDTPO 5 NAOH 3 Boric 10 3
.times. 10.sup.10 7 .times. 10.sup.10 4 .times. 10.sup.10 6 .times.
10.sup.10 acid Comparative 7 EDA 1 KOH 4 -- 13 4 .times. 10.sup.13
2 .times. 10.sup.13 5 .times. 10.sup.13 9 .times. 10.sup.10 Example
1 8 EDA 1 TMAH 0.2 CHES 9 8 .times. 10.sup.13 1 .times. 10.sup.13 3
.times. 10.sup.13 2 .times. 10.sup.11 9 DETA 3 -- -- -- 10 6
.times. 10.sup.12 1 .times. 10.sup.13 2 .times. 10.sup.14 3 .times.
10.sup.11 10 -- -- TMAH 0.4 CHES 9 8 .times. 10.sup.12 3 .times.
10.sup.13 3 .times. 10.sup.14 8 .times. 10.sup.10 11 -- -- KOH 1 --
13 3 .times. 10.sup.13 2 .times. 10.sup.13 4 .times. 10.sup.14 4
.times. 10.sup.11 12 -- -- -- -- -- 7 5 .times. 10.sup.13 2 .times.
10.sup.13 3 .times. 10.sup.14 8 .times. 10.sup.12
[0060] As obvious from the results in Table 1, by cleaning with a
liquid cleaner of the present invention, residual amount of
impurity metal at the silicon wafer surface can significantly be
reduced.
Example 2
[0061] In cleaning silicon wafer contaminated with Fe, Cu, Al and
Ca, prepared similarly as in Example 1, by brush-scrub cleaning
using a brush made of polyvinyl alcohol, a solution obtained by
diluting to 10 to 100 times with adding the liquid cleaner of the
present invention having each composition of No. 16 to No. 22
described in Table 2 to pure water was sprayed. Treatment
temperature was at 25.degree. C. and cleaning time was for 1
minute. After cleaning, silicon wafer was rinsed with ultra-pure
water, followed by drying with a spin dryer, amounts of impurity
metals remained at the silicon wafer surface was measured by the
similar method as in Example 1. Results are shown in Table 2.
Comparative Example 2
[0062] In cleaning silicon wafer contaminated with Fe, Cu, Al and
Ca, prepared similarly as in Example 1, by brush-scrub cleaning
using a brush made of polyvinyl alcohol, a solution obtained by
diluting to 10 to 100 times with adding a liquid cleaner having
composition of No. 23 to No. 25 described in Table 2 to pure water
or ultra-pure water (No. 26) was sprayed and treated similarly as
in Example 2. Then, amounts of impurity metals remained at the
silicon wafer surface was measured by similar method as in Example
1. Results are shown in Table 2. TABLE-US-00002 TABLE 2 Chelating
Conc. Alkaline Conc. Buffering Cleaning effect (atms/cm.sup.2) No.
agent (%) compound (%) agent pH Fe Cu Al Ca Example 2 13 EDTPO 0.5
KOH 2 -- 13 3 .times. 10.sup.9 8 .times. 10.sup.8 5 .times.
10.sup.9 6 .times. 10.sup.9 14 DEPPO 1 KOH 3 -- 13 1 .times.
10.sup.10 9 .times. 10.sup.9 3 .times. 10.sup.9 2 .times. 10.sup.10
15 EDTPO 1 KOH 0.1 CHES 9 1 .times. 10.sup.9 3 .times. 10.sup.9 8
.times. 10.sup.9 6 .times. 10.sup.9 16 TETHP 2 NaOH 5 -- 13 4
.times. 10.sup.10 1 .times. 10.sup.10 6 .times. 10.sup.10 3 .times.
10.sup.10 Comparative 17 EDA 1 KOH 1 -- 12 2 .times. 10.sup.13 8
.times. 10.sup.12 4 .times. 10.sup.13 7 .times. 10.sup.10 Example 2
18 DETA 1 TMAH 0.1 CHES 9 8 .times. 10.sup.13 3 .times. 10.sup.13 7
.times. 10.sup.12 9 .times. 10.sup.10 19 -- -- KOH 1 -- 13 8
.times. 10.sup.13 3 .times. 10.sup.13 7 .times. 10.sup.12 9 .times.
10.sup.10 20 -- -- -- -- -- 7 4 .times. 10.sup.12 8 .times.
10.sup.12 5 .times. 10.sup.13 3 .times. 10.sup.11
[0063] As obvious from Table 2, also by physical cleaning using
liquid cleaners of the present invention, residual amount of
impurity metal can significantly be reduced.
Example 3
[0064] Cu wiring is used in the next generation semiconductor. In
this case, to study damage of Cu wiring by cleaning agent used in
cleaning based on Cu dissolution amount, liquid cleaners No. 27 to
No. 32 of the present invention described in Table 3 was diluted to
10 to 100 times by adding pure water. Cu plated film was dipped in
thus obtained solutions at 25.degree. C. for 30 minutes to measure
an amount of dissolved Cu ions by an ICP-AES method. Amounts of
dissolved Cu are shown in Table 3. These amounts correspond to
damage degree to Cu wiring.
Comparative Example 3
[0065] The liquid cleaners shown by No. 33 to No. 35 in Table 3
were prepared by replacing a chelating agent of the present
invention with EDTA and DTPA, which were diluted 10 to 100 times by
adding pure water. Cu plated film was dipped in thus prepared
solutions at 25.degree. C. for 30 minutes to measure amount of
corroded and dissolved Cu ions by an ICP-AES method. Results are
shown in Table 3. TABLE-US-00003 TABLE 3 Chelating Conc. Alkaline
Conc. Buffering Amount of No. Agent (%) compound (%) agent pH
dissolved Cu (ppm) Example 3 21 EDTPO 0.5 KOH 0.3 -- 11 0.8 22
DEPPO 1 KOH 3 -- 13 0.5 23 DEPPO 2 KOH 0.1 CHES 9 1.2 24 TETHP 2
NaOH 5 -- 13 1.5 Comparative 25 EDTA 1 KOH 0.3 CHES 10 5.3 Example
3 26 EDTA 2 TMAH 1 -- 13 5.8 27 DTPA 2 TMAH 1 -- 13 4.1
[0066] As obvious from Table 3, a liquid cleaner of the present
invention provides less amount of dissolved Cu than cleaning agents
using EDTA or DTPA which is the conventional chelating agents and
thus less damage to Cu wiring.
INDUSTRIAL APPLICABILITY
[0067] A liquid cleaner of the present invention is composed of as
described above, therefore it provides effects of efficient removal
of fine particles or impurities derived from various metals at the
semiconductor substrate surface, even when used after a process
adopting an alkaline polishing agent or alkaline etching liquid,
without generating problems of causing difficult-to-remove gelled
particles at the substrate surface or easy generation of rough
semiconductor substrate surface.
* * * * *